Lattice contraction and lattice deformation of UO 2  and ThO 2  doped with Gd 2 O 3

Baena, A. R. C.; Cardinaels, Thomas; Govers, Kevin; Pakarinen, Janne; Binnemans, Koen; Verwerft, Marc

doi:10.1016/j.jnucmat.2015.09.018

Cited by 21 publications

(11 citation statements)

References 27 publications

(46 reference statements)

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“…A bond valence sum (BVS) assessment was made to evaluate the validity of the introduction of a cluster distortion parameter δ. , The BVS analysis has been successfully applied in the investigation of complex uranium oxides and fluorides for more than 60 years already. − With the atomic coordinates in the expanded unit cell (see Table ), BVS calculations were performed for different values of the deformation parameter δ and with the parameter sets ( R 0 and b ) published by Zachariasen . The parameter sets published by Brese and O’Keeffe, and Brown, provided almost identical results. , …”

Section: Resultsmentioning

confidence: 99%

Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction

et al. 2016

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Polycrystalline UO powder was synthesized by oxidation of UO powder under controlled conditions using in situ thermal analysis, and by heat treatment in a tubular furnace. The O/U ratio of the UO phase was measured as 2.34 ± 0.01. The crystal structure was assessed from X-ray diffraction (XRD) and selected-area electron diffraction (SAED) data. Similar to UO (more precisely UO), UO exhibits a long-range ordered structure, which is closely related to the fluorite-type arrangement of UO. Cations remain arranged identical to that in the fluorite structure, and excess anions form distorted cuboctahedral oxygen clusters, which periodically replace the fluorite anion arrangement. The structure can be described in an expanded unit cell containing 15 fluorite-like subcells (UO), and spanned by basis vectors A = a - 2b, B = -2a + b, and C = 3c (lattice parameters of the subcell are a = b = 538.00 ± 0.02 pm and c = 554.90 ± 0.02 pm; c/a = 1.031). The arrangement of cuboctahedra in UO results in a layered structure, which is different from the well-known UO crystal structure.

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Section: Resultsmentioning

confidence: 99%

Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction

et al. 2016

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“…The data are fitted to linear equations to determine the radii of U 4,8 , Ln 3,8 , and U 5,8 ,. The experimental data are from (La) Hill (Hill, 1962), Stadlbauer et al (Stadlbauer et al, 1974), Preiur et al (Prieur et al, 2018); (Pr) Yamashita et al (Yamashita et al, 1985); (Nd) Une and Oguma (Une and Oguma, 1983a), Ohmichi et al (Ohmichi et al, 1981), Fukushima et al (Fukushima et al, 1983); (Gd) Baena et al (Baena et al, 2015), Ohmichi et al (Ohmichi et al, 1981), Cardinaels et al (Cardinaels et al, 2012), Leyva et al (Leyva et al, 2002), Fukushima et al (Fukushima et al, 1982), Hirai and Ishimoto (Hirai and Ishimoto, 1991), Soldati et al (Soldati et al, 2016). (Yamashita et al, 1985) (circles and squares are the samples synthesized at 1623 K), Lynds et al (Lynds et al, 1963) (open down triangles), Belbeoch (Belbeoch et al, 1964) (shaded down triangles), Matsui and Naito (Matsui and Naito, 1975) (open up triangles), Schaner (Schaner, 1960) (left triangles), Grønvold (Grønvold, 1955) (shaded up triangles).…”

Section: Thermodynamic Modelmentioning

confidence: 99%

Thermodynamic and Structural Modelling of Non-Stoichiometric Ln-Doped UO2 Solid Solutions,Ln = {La, Pr, Nd, Gd}

et al. 2021

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Available data on the dependence of the equilibrium chemical potential of oxygen on degrees of doping, z, and non-stoichiometry, x, y, in U1-zLnzO2+0.5(x-y) fluorite solid solutions and data on the dependence of the lattice parameter, a, on the same variables are combined within a unified structural-thermodynamic model. The thermodynamic model fits experimental isotherms of the oxygen potential under the assumptions of a non-ideal mixing of the endmembers, UO2, UO2.5, UO1.5, LnO1.5, and Ln0.5U0.5O2, and of a significant reduction in the configurational entropy arising from short-range ordering (SRO) within cation-anion distributions. The structural model further investigates the SRO in terms of constraints on admissible values of cation coordination numbers and, building on these constraints, fits the lattice parameter as a function of z, y, and x. Linking together the thermodynamic and structural models allows predicting the lattice parameter as a function of z, T and the oxygen partial pressure. The model elucidates contrasting structural and thermodynamic changes due to the doping with LaO1.5, on the one hand, and with NdO1.5 and GdO1.5, on the other hand. An increased oxidation resistance in the case of Gd and Nd is attributed to strain effects caused by the lattice contraction due to the doping and to an increased thermodynamic cost of a further contraction required by the oxidation.

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“…This potential was therefore selected for this study; its short range parametrization is reported in Table 1. In UO2, hole electronic defects are generally thought to maintain the system charge neutral [32]. In the present study, holes were described as localised on the uranium sublattice as uranium atoms with a (5+) charge.…”

Section: Atomic Scale Simulationsmentioning

confidence: 84%

Atomic scale analysis of defect clustering and predictions of their concentrations in UO2+x

Caglak

Govers

Lamoen

et al. 2020

Journal of Nuclear Materials

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Lattice contraction and lattice deformation of UO 2 and ThO 2 doped with Gd 2 O 3

Cited by 21 publications

References 27 publications

Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction

Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction

Thermodynamic and Structural Modelling of Non-Stoichiometric Ln-Doped UO2 Solid Solutions,Ln = {La, Pr, Nd, Gd}

Atomic scale analysis of defect clustering and predictions of their concentrations in UO2+x

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Lattice contraction and lattice deformation of UO 2 and ThO 2 doped with Gd 2 O 3

Cited by 21 publications

References 27 publications

Assessment of the U3O7 Crystal Structure by X-ray and Electron Diffraction

Assessment of the U3O7 Crystal Structure by X-ray and Electron Diffraction

Thermodynamic and Structural Modelling of Non-Stoichiometric Ln-Doped UO2 Solid Solutions,Ln = {La, Pr, Nd, Gd}

Atomic scale analysis of defect clustering and predictions of their concentrations in UO2+x

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Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction

Assessment of the U₃O₇ Crystal Structure by X-ray and Electron Diffraction